This invention relates to a method of cleaning plasma chambers used for processing semiconductor wafers and, more particularly, a method of cleaning such plasma chambers utilizing a universal cleaning wafer suitable for use with an electrostatic clamping chuck or a mechanical clamping chuck.
Plasma processing of semiconductor wafers involves the performance of one or more plasma processes such as gas chemistry etching, or chemical vapor deposition on one or more semiconductor wafers within the plasma chamber. As the geometries of semiconductor devices become smaller, the ability to maintain the uniformity and accuracy of critical dimensions becomes strained. Many of the processes carried out within semiconductor processing reactors leave contaminant deposits throughout the process chamber which accumulate and become the source of particulate matter harmful to the creation of a semiconductor device. The non-volatile particulate matter tend to remain inside the plasma chamber in the form of loosely attached particles to the various element surfaces of the plasma chamber. As the dimension size of the semiconductor device has become smaller, the presence of particulate matter upon the surface of the semiconductor wafer has become more of a risk factor. Consequently, the cleanliness of plasma processing chambers (i.e., plasma etching, reactive ion etching (RIE), plasma enhanced chemical vapor deposition (PECVD), etc.) is critical.
Removal of contaminants from the various surfaces inside a plasma chamber has been accomplished by periodically cleaning the plasma chamber. Known cleaning methods have involved opening the plasma chamber, disassembling portions of the chamber, and removing the contaminant deposits by physical or chemical methods. Such cleaning methods are complicated, disruptive, time consuming and can be the source of additional contamination.
Recognizing the disadvantages of disassembling the plasma chamber for cleaning, it has been proposed in Law et al. U.S. Pat. Nos. 4,960,488, Cheung et al. 5,158,644, and Shufflebotham et al. 5,503,676, the disclosures of which are incorporated by reference herein, to use an etching plasma to self-clean the plasma chamber. The gas used in the self-cleaning is chosen so as to chemically react with the particulate matter and vaporize it but at the same time avoiding damage to the chamber hardware. Su et al. U.S. Pat. No. 5,507,874, the disclosure of which is incorporated by reference herein, is similar to the above references but the teaching is directed to the cleaning of an electrostatic chuck.
Kilburn et al. U.S. Pat. No. 5,240,555, the disclosure of which is incorporated by reference herein, discloses a cleaning wafer that is used during the self-cleaning of an etching machine. The purpose of the cleaning wafer is to activate the radio frequency power which is used to create the cleaning plasma. The cleaning wafer is made from the same material as the interior of the etching machine to avoid contamination by foreign elements. The cleaning wafer could be aluminum as disclosed by Kilburn et al. or any of a wide variety of unspecified materials.
Electrostatic chucks are devices for holding or clamping semiconductor wafers during plasma manufacturing processes. An electrostatic chuck secures the entire lower surface of a semiconductor wafer by Coulombic force and provides an alternative to mechanical clamping of the semiconductor wafer to the support platform or pedestal. A clear advantage in using an electrostatic chuck is that it eliminates the need for mechanical clamping mechanisms, which physically contact the front of the wafer inducing contamination on the surface of the wafer. Additionally, when a semiconductor wafer is secured to the electrostatic chuck, the flatness of the semiconductor wafer is improved, improving things like the across wafer thermal cooling.
While the Kilburn et al. aluminum cleaning wafer would work with an electrostatic chuck, it would not be inert to many cleaning plasmas. Assuming that Kilburn et al.s cleaning wafer could be made of a different material, such as ceramic, a ceramic cleaning wafer would not work with an electrostatic chuck although it would be inert to many cleaning plasmas.
Thus, a problem with the Kilburn et al. cleaning wafer is that it is not suitable for electrostatic chucks while also being resistant to the cleaning plasma.
It is accordingly a purpose of the present invention to have a universal cleaning wafer that is both inert to many cleaning plasmas and that is usable with an electrostatic chuck.
It is another purpose of the present invention to have a universal cleaning wafer that is suitable for use with both electrostatic chucks and mechanical chucks.
These and other purposes of the invention will become more apparent after referring to the following description of the invention in conjunction with the accompanying drawings.